The electrical resistance and compressive strength were measured to gain a better under- standing of the sintering characteristics of low-rank coal ashes involved in deposit formation in combustion systems. Low-rank coal ashes were prepared by the standard ASTM ashing procedures at 750℃ and then separated into three different particle size fractions. The sinter point determined by the electrical resistance method decreased with decreasing particle size at three different particle size fractions of each coal ash. The compressive strength test was made as a function of temperature in the range 750-950℃. At a given sintering temperature, strength of the sintered ash was inversely proportional to particle size. For any given particle size of each coal ash, the strength increased with increasing sintering temperature. X-ray diffraction of the sintered coal ashes showed that, as sintering temperature increased, there was an inverse relationship between sinter strength and the amount of anhydrite in the sintered ash, and a direct relationship between strength and the amount of hauyne.